A Shift from Second to Third-Generation Fighter Aircraft

Jet fighters are often categorized historically in terms of “generations”. Fierce disputes never cease between experts, amateurs, and others without any expertise on the subject as to which generation a particular fighter must be referred to. Currently, it is the fifth post-war generation of jet fighters that is apparently on the receiving end of criticism.

These disputes, however, are often only for the sake of argument because any jet fighters being compared are designed to pursue totally different objectives. After all, the world has still not agreed on any generally-accepted criteria for the classification of jet fighters by generation. Or rather, we do have that set of criteria, but the value of each element within that set is constantly changing. For that reason, jets are often moved up and down the “generations” ladder. When an aircraft fails to fit the five-generation classification system, variants like “4+” or even “4++” are adopted without a shadow of a doubt.

But do we need all that “generations” stuff anyway? After all, the outcome of any dogfight depends on a variety of parameters that characterize the combat capabilities of not just an aircraft alone, but of a whole complex of hardware in which a jet fighter is but a “tiny screw” in a large, highly sophisticated mechanism. An important one, but only a screw. Therefore, it is not a good idea to reduce victories and defeats in air battles to only the technological marvel implemented in the individual fighters. A worse idea would be to evaluate that marvel on a five-point scale. And considering the fact that representatives of only two adjacent generations are normally in active force, the idea to use a two-point scale doesn’t sound absurd, either.

But, of course, we do need a technology evaluation tool. Because in a real battle, under otherwise equal conditions, the outcome of an encounter in the air may depend exactly on the performance characteristics of an aircraft. We also need a tool for measuring technological advancement. A tool that would equally assess our own vehicles and the vehicles of potential adversaries to establish technological superiority or, vice versa, inferiority. Then appropriate decisions can be made—design a new jet fighter, upgrade and retrofit, ramp up the existing fighter count, or “that’ll do as is”. Since such decisions are made, as a rule, by politicians and economists, i.e. by people who are far from the science of warfare, it is highly desirable to reduce all data to a single numerical index. E.g., let’s assign the “1” index to the F-16A fighter. In that case, our Article 38-18 and Article 9-12 aircraft would be “0.7” and “1.15”, respectively. To carry out such an evaluation of the combat capabilities of a jet fighter, experts rely on aggregated factors like ratios of the military’s technology level. Many lances were broken over these ratios, and even more over the question of whether the F-35 may or may not be designated as a fifth-generation fighter.

Today, a jet fighter is a complex, highly sophisticated weapon system. In the past, mechanisms were not that complicated, and all differences were evident to an unaided eye, with no need for any abstruse ratios. Generations of fighters were easier to single out.

What was the most valuable aspect of a fighter aircraft during the “classical” air battles period? What did engineers compete for during the two world wars?

Speed.

Why speed? To answer that question, let’s imagine an air battle. A fighter aircraft has to destroy an enemy plane and avoid getting destroyed first. But how? Probably the best description for this process comes from one of the famous tactical maxims of Aleksander Ivanovitch Pokryshkin (“Altitude—Speed—Maneuvering—Fire”). Altitude allows for gaining speed; speed is key to successful maneuvering (or disengaging after a failed attack); maneuvering makes it possible to open fire to ultimately destroy your target.

However, in this historical period, “fire” could be bracketed out because the armaments carried by fighters of the opposing sides were comparable. So, only altitude, speed, and maneuvering remain. Interestingly, “speed” is mentioned in the other two parameters of Pokryshkin’s formula. Altitude is the opposite side of speed. By exchanging the kinetic energy of an aircraft for potential energy, we can gain altitude as our speed increases, and vice versa. This “energy exchange” is where the lion’s share of combat maneuvering—the third element of the formula— comes from.

It turns out that speed is the integral indicator that characterizes the suitability of a fighter aircraft for air combat.

How did speed change over time, you may ask? Here you are:

An intriguing graph, isn’t it? The idea of singling out “generations” of fighter aircraft came around in the natural course of events. Those were real generations, unlike the conditional ones we use today.

The shift from the first to the second generation occurred as early as during World War I. It was associated with the emergence of fighter aircraft and the appearance of aerobatic maneuvering as an element of an air battle. The Fokker Scourge, the achievements of Max Immelmann, Pyotr Nesterov, Oswald Boelcke, and Roland Garros all appear on the bright, well-known pages of history.

Right now, we are primarily interested in the shift from the second to third generation. It occurred during a peaceful time, and we are convinced that it didn’t receive any adequate, though well-deserved, coverage. As a result, a lot of speculation has grown around the issue. Let’s have an up-close look at this transfer with general information followed by specific examples.

The classic fighter aircraft of the final phase of World War I was a wood-and-fabric biplane with a 200 hp engine and a take-off weight of less than one ton. Typically, the armament they carried included a pair of rifle-caliber machine guns.

The war came to an end, bringing the development of warfare technologies to a halt. This, however, did not have any effect on the technological progress. New stimulus to progress came from the rapid development of civil aviation as well as from massive enthusiasm about airsports and record breaking.

In the first years after the end of the war, typical civil planes were converted war aircraft—decommissioned reconnaissance planes, bombers, and other vehicles that were “excessive” in a peaceful time. The first passengers were wrapped in fur coats, seated in the places of flight observers and gunners, their luggage loaded (or suspended) instead of bombs—and voilà! An airliner was at their service! The invisible hand of the market quickly showed the newborn commercial air carriers a direction for the further development of their aircraft. Aircraft designers, in turn, rushed to fulfill their requests with maximum zeal and zest. At that time, military orders were almost completely gone, and civil orders were so scarce they were treated like precious gems. At the same time, designers had to come up with something radically superior to the converted aircraft that flooded the market after the war.

Several major niches emerged—passenger aircraft (divided into several segments by the range of flight and passenger capacity), freight aircraft, and airmail carriers. Engineers realized the advantages of a monoplane scheme quite quickly. All things being equal, a monoplane is heavier than a biplane. But at the same time, it’s more economical because less energy is “wasted” overcoming the resistance of air (drag). Therefore, it can carry freight and passengers over a longer distance in less time. Of course, to achieve that, you have to sacrifice other qualities. For example, the take-off and landing characteristics will be impacted. But for civil aviation that is “tied” to large cities one way or another, it is not a crucial aspect. If needed, you can always build a larger airport with a smoother runway. A new generation of engines, further progress in aerodynamics, metallurgy, and materials resistance took civil aviation to a new level of economic efficiency.

These conclusions were proved by airports, in particular. All records related to range and speed gradually shifted from biplanes to monoplanes.

And then all of a sudden it turned out that a sort of backwards conversion was also possible. The objectives of civil aviation—transporting as much as possible as far and as quickly as possible—corresponded to the objectives of bombers. Increasing flight range made it possible to “reach” targets located deep in the enemy’s rear and push allied airfields further into the safe zone, while an ever-increasing speed left the enemy’s AA defenses with fewer chances to successfully intercept targets. In the early 30s, the appearance of the American B-10 contributed to the emergence of a new generation of bombers. In a few years’ time, the Soviet SB, British Hampden, Whitley and Wellington, German He-111 and Do-17, and Japanese Type 96 land-based attack aircraft and Type 97 heavy bomber (in common parlance, G3M and Ki-21, respectively), etc. took to the skies. They were high-speed, aerodynamically “clean” monoplanes with cantilever wings and retractable landing gear.

And then a paradoxical situation arose—the means of air attack drastically outpowered the means of air defense. At that time, fighter aircraft fleets were still predominantly composed of light biplanes, which could hardly boast any serious operational superiority over the aircraft of the end of World War I. Yes, engines became stronger, but this strength could not add anything to the operational capabilities of an aircraft, owing to the specifics of the biplane design itself.

So, why was the second main wing an obstacle? A wing is a source of lift force that keeps an aircraft in the air. At first glance, lift force is directly dependent on the speed of an aircraft and the surface area of its wings. At a sufficiently high speed, the extra wing surface of a biplane becomes irrelevant. At a high speed, the second wing, and its fastening elements like braces and struts, in fact, transform into a source of parasitic drag. With a reduced wing area, an aircraft cannot stay in the air at low speeds but acquires the ability to fly much faster.

But why did monoplanes fail to achieve worldwide acceptance right from the start? Well, frankly, they did, but for a very limited time. The first specialized mass-produced fighter aircraft appeared in 1915. It was the German Fokker E.I (“E” stands for “eindekker” meaning “monoplane” in German).

However, the bomber was quickly outmatched by biplane fighters. What exactly were they better at?

First of all, the climb speed. The more powerful the lift force, the faster a plane can gain altitude, win the height, and gain an advantage over an enemy aircraft even before the air battle begins. Do you remember that the first element in Pokryshkin’s formula of success is altitude? This was the underlying reason for the bright, yet short-lived, performance of triplane fighters at the fronts of World War I. Despite the slow speed, lack of stability, and overall fragility of those aircraft, they allowed pilots to secure the right to be the first to open fire in an air battle.

Another important factor is horizontal maneuverability. To adjust the direction of the flight, pilots use flight control surfaces (ailerons) to produce a banking movement, and the wing lift acts in a sideways (as opposed to upward) direction. The more lift a pilot has at their discretion, the larger the share of it that can be used to make a maneuver, and the more efficient the turn will be.

It turns out that the pros of a biplane include two of the “success formula” elements—Altitude and Maneuvering—while the cons include only one—Speed. It is, therefore, no surprise that the biplane scheme had prevailed for quite a while. For example, Nikolai Polikarpov, a Soviet aeronautical engineer who designed the first mass-produced 3rd generation fighter I-16, always advocated an idea of having two types of fighters in active service, a high-speed monoplane and a maneuverable biplane.

But we remember that it’s not only the lift force of the wing that we can use to gain height and effectively maneuver, we can also achieve this by utilizing our reserve of kinetic energy, that is, speed. However, in the mid 30s this definitely wasn’t an obvious fact.

And it’s not only maneuverability that mattered. As we have already mentioned, the transition to a monoplane scheme inevitably affected the take-off and landing characteristics of aircraft, allowing planes to fly fast at the expense their ability to fly slowly. As a result, landing has to be performed at a higher speed, too. The invention of high-lift devices simplified the problem but didn’t solve it. It was soon apparent that new aircraft wouldn’t be able to take off from the first available more or less flat field—new dedicated airfields would have to be built, even for small and lightweight fighters. A potential enemy would become aware of such airfields and try to attack them, which meant the airfields would need protection. A high-speed airplane would be more sophisticated structurally, which meant new workshops would be needed to service them. And new qualified staff. As we know, it’s people who make all the difference! A high-speed fighter is more difficult to control and requires a pilot with a higher level of education and training. Educational institutions and special trainer aircraft are needed. We need new gun sights to be able to hit something at such speeds. This chain of demands is endless, and each of its links requires costs to be incurred.

Such costs are by all means justified. But understanding this required not just designing new generation fighter planes, but drafting new tactics of their application, new approaches to air combat, and a whole new ideology of a fighter aircraft.

And nowhere was it more apparent than in sea-based aviation.

In the mid 30s, towards the end of the era of the “second generation” fighter aircraft, the three strongest maritime nations—Great Britain, USA, and Japan—could boast having aircraft carriers in active service. Fighters based on all those carriers possessed common features. Great Britain had the Hawker Nimrod and Hawker Osprey. The USA and Japan had the Grumman F2F and Nakajima A4N, respectively. Those were the newest models at that time. Lightweight but slower biplanes. And that made sense. You can build an aerodrome with the longest runway on land, but at sea you are limited by the size of your carrier, her docks and channels, your money—and common sense. An all-metal monoplane had looked out of place onboard an aircraft carrier until sophisticated high-lift devices were developed. By the mid 30s, it was already a realistic task. At that time, strong doubts were expressed by all fleets as to the necessity of having fighters on carriers at all. Those were justified doubts.

Why? Find out from our next article titled “A Shift from Second to Third-Generation Fighter Aircraft: Great Britain”.